Reservoir systems for administering multiple populations of particles

ABSTRACT

Various particle reservoir systems are described which utilize one or more traveling wave grids within a reservoir to selectively transport particles to a reservoir exit. The reservoir systems are uniquely adapted for use with a variety of print head configurations.

BACKGROUND

The present exemplary embodiment relates to the dispensing oradministration of two or more populations of particles. It findsparticular application in conjunction with the printing arts, and willbe described with particular reference thereto. However, it is to beappreciated that the present exemplary embodiment is also amenable toother like applications such as the pharmaceutical processing ofmedication as in the “printing” of pills.

BRIEF DESCRIPTION

In accordance with one aspect of the present exemplary embodiment, areservoir system adapted for use in a printing system is provided. Thereservoir system comprises a reservoir body defining an interior hollowregion adapted to store particles and a channel. The hollow region andthe channel are in flow communication through a particle feed exit. Thereservoir system also comprises a traveling wave grid assembly disposedwithin the interior hollow region. The traveling wave grid assembly isadapted to transport particles in the hollow region defined in thereservoir body to a location proximate the particle feed exit. Thetraveling wave grid assembly includes a non-planar traveling wave gridthat serves to recirculate and provide a continuous, or nearly so,supply of particles to the location proximate the particle feed exit.

In accordance with another aspect of the present exemplary embodiment, areservoir system is provided which is adapted for use in a printingsystem. The reservoir system comprises at least one member defining ahollow flow channel terminating at a channel exit. The reservoir systemalso comprises a collection of reservoir bodies, in which each reservoirbody defines an interior hollow region adapted to store particles. Thehollow region in the hollow flow channel are in flow communicationthrough a particle feed exit. The reservoir system also comprises acollection of traveling wave grids. At least one of the collection oftraveling wave grids is disposed within the interior hollow region of acorresponding reservoir body and positioned and configured to transportparticles in the hollow region of the corresponding reservoir body to alocation proximate the particle feed exit.

In accordance with yet another aspect of the present exemplaryembodiment, a reservoir system adapted for use in a printing system isprovided. The reservoir system comprises a collection of reservoirbodies, in which each body defines an interior hollow region adapted tostore particles. The reservoir system also comprises a collection ofcorresponding gas channels. Each gas channel is dedicated to arespective reservoir body and in flow communication therewith through aparticle feed exit. The reservoir system also comprises a collection ofcorresponding traveling wave grids. Each traveling wave grid is disposedin an interior hollow region defined within a respective reservoir body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a printing system utilizing an exemplaryembodiment reservoir system.

FIG. 2 is a schematic of an exemplary embodiment reservoir system.

FIG. 3 is a graph illustrating a voltage waveform for use in anexemplary embodiment reservoir system.

FIG. 4 is a schematic of an exemplary embodiment reservoir system.

FIG. 5 is a schematic of another exemplary embodiment reservoir system.

FIG. 6 is a schematic of another exemplary embodiment reservoir system.

FIG. 7 is a schematic of yet another exemplary embodiment reservoirsystem.

FIG. 8 is a schematic of another exemplary embodiment reservoir system.

DETAILED DESCRIPTION

The exemplary embodiment provides systems and techniques for thestorage, transport, and controlled distribution of small particles suchas for example, toner particles. Although the exemplary embodiment isdescribed in terms of the printing arts and transporting tonerparticles, it is to be understood that the exemplary embodiment includesother applications involving the storage, transport, or distribution ofminute particles.

Several exemplary embodiment print head configurations are describedherein. These print head configurations are particularly adapted for usein a powder ballistic aerosol marking (BAM) printer that can image ontoan intermediate substrate or be used as a direct marking device. Theexemplary embodiment print head configurations include single-shotcolor, two-shot color, and tandem color. A significant feature of theexemplary embodiment is the provision and incorporation of a multi-piecetraveling wave grid for recirculating transport and cascade delivery oftoner to one or more gating aperture arrays for on demand printing.

The term “traveling wave grid” as used herein collectively refers to asubstrate, a plurality of traveling wave electrodes to which a voltagewaveform is applied to generate the traveling wave(s), and one or morebusses, vias, and electrical contact pads to distribute the electricalsignals (or voltage potentials) throughout the grid. The term alsocollectively refers to one or more sources of electrical power, whichprovides the multi-phase electrical signal for operating the grid. Thetraveling wave grids may be in nearly any form, such as for example aflat planar form, or a non-planar form. Traveling wave grids, their use,and manufacture are generally described in U.S. Pat. Nos. 6,351,623;6,290,342; 6,272,296; 6,246,855; 6,219,515; 6,137,979; 6,134,412;5,893,015; and 4,896,174, all of which are hereby incorporated byreference.

Ballistic aerosol marking (BAM) is a technology being developed for highspeed direct marking onto paperoronto an intermediate medium. BAM useshigh-speed continuous gas jets to move small toner particles to theprint medium. The toner is electrostatically gated on demand fromapertures transverse to the gas channel. The print head is comprised ofan array of individually controlled micro-channels, each of which is aLaval nozzle incorporating a Venturi structure (converging/divergingchannel) to accelerate and focus the narrow gas jets. BAM is designed tobe a true color CMYK printing system, whereby metered amounts ofcomponent colors for individual nozzles are injected on-demand into thejet stream at the same time to be conveyed to the print medium. Aschematic of the process is shown in FIG. 1. Details and informationrelating to ballistic aerosol marking systems, components, and processesare described in the following U.S. Pat. Nos. 6,751,865; 6,719,399;6,598,954; 6,523,928; 6,521,297; 6,511,149; 6,467,871; 6,467,862;6,454,384; 6,439,711; 6,416,159; 6,416,158; 6,340,216; 6,328,409;6,293,659; and 6,116,718; all of which are hereby incorporated byreference.

Specifically, FIG. 1 illustrates a BAM printing apparatus 100 comprisinga member 110 defining a hollow channel 120. As noted, the channel 120 isin the form of a Laval type expansion pipe through which pressurized gasflows, as indicated by arrow 140. The channel 120 includes a narrowedregion 130, which is upstream of one or more feed apertures describedbelow. The channel 120 terminates at an exit 150 at which the exitinggas flow, indicated by arrow 170, is discharged from the member 110. Theapparatus 100 further comprises one or more toner supply andadministering devices designated for example as 160 a, 160 b, 160 c, and160 d through which toner types C, M, Y, and K are administered,respectively. Referring to device 160 a for toner type C, for example,the toner is selectively delivered through a feed line 162 a and exitsat a venturi toner feed or pressure forced feed exit 164 a. Control oftoner through each of the devices 160 a, 160 b, 160 c, and 160 d can beprovided by an electrostatic toner gate. During operation of theapparatus 100, a flow 140 of highly pressurized gas, for example CO₂ at72 atmospheres, enters the channel 120 and specifically, the narrowedregion 130. Toner is entrained in the gas flow as the flow passes thevarious toner feed exits, for example 164 a. The pressure of the gasflow is reduced upon entering the expanded region of the channel 120prior to the exit 150. As the gas leaves the exit 150, its pressure isfor example, about 1 atmosphere. This is significant in that it resultsin the gas reaching its fully expanded volume. The exiting gas flow 170is a focused, high velocity aerosol jet. Fusing of toner entrained inthe flow can occur on impact with a substrate, such as 180, or fusingmay occur while toner is in flight.

Although a high pressure gas at 72 atmospheres is noted, the exemplaryembodiment reservoir systems can utilize high pressure gas sources atpressures less than or greater than that noted.

This technology can utilize high viscosity inks to minimize inter-colorbleed. Since it is designed as a single-pass print engine, there is noadditional requirement for color registration. Images are formed whenthe individually controlled micro-channels combine to lay down thecomponent image patterns. Although in theory toners may be designed forkinetic fusing on impact, a working compromise is to lower gas pressureand optimize toner morphology together with paper preheat or printmedium surface treatments to minimize backscatter or bounce-back of thetoner on impact.

Continuous line printing has been successfully demonstrated using anexemplary embodiment reservoir system. On demand gating into a 8×macro-channel and subsequent pixel printing has also been experimentallydemonstrated using an exemplary embodiment reservoir system. In thelatter, a re-circulating toner supply mechanism is fabricated using atraveling wave grid disposed on or about an Ultim roll for travelingwave transport and fluidization of the toner. FIG. 2 shows a schematicview of a toner re-circulating flow cell 200 in accordance with theexemplary embodiment. Specifically, the cell 200 comprises a body orenclosure 210 for housing or otherwise retaining toner, designated as atoner sump 220. The enclosure 210 also comprises an apertured plate 230disposed along one of its faces. The cell additionally includes a member240, which in the exemplary embodiment depicted in FIG. 2 is acylindrical or roll member. The member 240 includes a region such as anouter circumferential surface about its periphery that includes atraveling wave grid 250. The cell 200 also comprises, or can be adaptedto interface with, a toner loading component 260, such as a solenoidactuator that is configured to supply toner to the cell upon actuationof the solenoid. Upon operation of the cell 200, the activation of thetraveling wave grid 250 transports toner from the sump 220 toward theapertured plate 230 in the direction of arrow A, at which the toner canbe withdrawn or otherwise deposited. Remaining toner on the grid 250 isreturned as shown by arrow B to the sump 220. The toner cloud resultingadjacent the traveling wave grid 250 in the cell 200 can be gated forexample, using 2-φ voltage signals through electrodes providing 50 umapertures fabricated from a gold coated 2-mil Kapton film. Theelectrodes could be disposed in the plate 230. A 4-phase circuit is usedto drive the traveling wave. These parameters are representative innature and variations can be utilized in the exemplary embodiment.

FIG. 3 shows two cycles and representative voltage patterns for thetraveling wave used in the exemplary embodiment. A 10 Hz wave frequencyinduces a toner wave velocity of 0.5 cm/s. The voltage pattern in FIG. 3was applied at a 90 degree phase separation, a percentage duty cycle(w/t) of 50%, a level of 400 V thereby producing a charge of −3.07 C, adensity of 0.811 gm/cm³, and an electrode spacing of 2.9 μm. Anexperimental implementation has been demonstrated for three flow cellscontaining magenta (Majestyk), and black and cyan emulsion aggregation(EA) toner, all sharing a single traveling wave grid. Toner transporthas been achieved on a non-planar traveling wave grid wrapped around anUltim roll. Striations were observed of cyan EA toner on the conductiveportions of the traveling wave grid, which is 8-mil pitch at 50% dutycycle. Additionally, gated toner was observed distributed around a 50 umaperture.

The incorporation of aperture arrays into flow cells enables theprovision of print head architectures that may be suitable for a BAMprinter. Various exemplary embodiments are described as follows:single-shot color, two-shot color, and tandem color.

An exemplary embodiment reservoir system for a single-shot colorconfiguration is shown schematically in FIG. 4. In this embodiment, asingle channel 320 utilizes four toner apertures, with twore-circulating toner cavities located on each side of the channel.Specifically, FIG. 4 depicts a single-shot color print head 300comprising a channel 320 in communication with a reservoir 310 a, 310 b,310 c, and 310 d; and a toner feed exit 312 a, 312 b, 312 c, and 312 ddefined therein. Each of the feeds 312 a-d administer toner to thechannel 320 through which a stream of gas, designated by arrow A, flows.The channel 320 generally extends from a source of high pressure gas(not shown) to a channel exit 322. The toner, carried or otherwiseentrained in the flow A, is subsequently deposited on a print medium350, such as a drum or belt. Disposed within each reservoir is at leastone traveling wave grid for transporting and in certain configurations,recirculating toner within the reservoir. The one or more traveling wavegrids transport toner or other particulates from a hollow region withina reservoir to a location near a toner feed exit. For example, a firsttraveling wave grid 314 a and a second traveling wave grid 316 a areprovided in reservoir 310 a. The first grid 314 a transports toner froma first region to a second region within the reservoir 310 a. The secondgrid 316 a transports toner within the reservoir 310 a, and ideally fromthe second region to the first region. During operation and transport oftoner within a reservoir, a toner “cloud” typically forms in proximityto each grid, such as shown for example by clouds 322 a and 324 a inFIG. 4.

To accommodate this single-shot CMYK configuration, a channel length ofabout 4 mm is utilized. “Channel length” as described herein isgenerally the distance from the location in the channel at which tonerfeed is suitably mixed, to the substrate or surface to which the toneris applied. Referring to FIG. 5, a schematic of an alternate exemplaryembodiment reservoir system for a single-shot print head 400 is shown.The print head 400 comprises a body 405 which defines a plurality oftoner reservoirs such as reservoir 410. A toner sump 420 is definedwithin the reservoir 410. A traveling wave grid member 430 transportstoner from the sump 420 to a channel 440 through which gas such as airflows. A source of high pressure 445 is provided upstream of thelocation in the channel 440 at which toner from a reservoir is fed.Toner exits the reservoir 410 through a feed 412 at which it enters thechannel 440. The toner is entrained or otherwise carried in the flowinggas stream in the channel 440 and subsequently deposited on a drum 450.A time delay in aperture gating can be utilized to allow for colorpremixing within the channel. Therefore, a major advantage is that colorregistration is not a problem. The channel 440 can be oriented to printupwards, for example up to 30 degrees from vertical, as gravity may be afactor for toner cloud generation and thus transport of the toner alonga traveling wave grid. Toner is electrostatically gated on-demand. Thetraveling wave grid 430 can be provided in two over-lapping sections. Insuch a multi-section configuration, unused toner falls back onto a lowergrid to be transported back to an upper grid. Toner in the flow cell isrefilled periodically from a main reservoir (not shown) using acontrolled transport mechanism.

The channel through which a flowing gas or medium travels and entrainsor otherwise receives particles such as toner, can be defined in thesame member or body as is defined the hollow reservoir. Alternately, thechannel can be defined in a separate component or body, apart from ordifferent than the reservoir.

In a two-shot color print head configuration, a print head is utilizedthat corresponds to the single-shot color configuration previouslydescribed, but with two channels and one toner supply on each side ofeach channel. Each channel has two re-circulating toner cavities, withone on each side. Full color requires two channels or two passes. Thisconfiguration allows the use of 2 mm channel lengths, and half thenumber of high voltage drivers. The channel can be utilized to printupward, up to 30 degrees from vertical, as gravity may be a factor fortoner cloud generation.

A portion of an exemplary embodiment reservoir system for a two-shotcolor configuration is shown schematically in FIG. 6. Referring to FIG.6, one half of a two-shot color print head 500 is shown. The portionshown comprises one channel, having reservoirs 510 a and 510 b; andtoner feed exits 512 a and 512 b defined therein. The channel 520extends from a source of high pressure gas (not shown) to a channel exit532. Each of the reservoirs include a toner supply cell with travelingwave grids for transporting toner from a sump to the feed exit. It willbe understood that for full color, two of the assemblies shown in FIG. 6are utilized. Specifically, reservoir 510 a includes a lower travelingwave grid 514 a which transports toner to an upper traveling wave grid516 a. Reservoir 510 b includes a lower traveling wave grid 514 b whichtransports toner to an upper traveling wave grid 516 b. During operationof the grids, toner clouds 522 a and 524 a reside on, and are generallytransported on, grids 514 a and 516 a, respectively. Similarly, tonerclouds 522 b and 524 b reside on, and are generally transported on,grids 514 b and 516 b, respectively. Each of the feeds 512 a and 512 badminister toner to a channel 520 through which a stream of gas,designated by arrow A, flows. The toner, carried or otherwise entrainedin the flow A, is deposited on a print medium 550 such as a drum orbelt.

An exemplary embodiment reservoir system for a tandem colorconfiguration is also provided. A tandem color configuration uses onere-circulating toner supply per channel, with one color per channel, andfour tandem channels for single pass color. FIG. 7 shows a quad printhead arrangement. Time delay is incorporated into the gating tosynchronize four color registration. Channel length may be 2 mm and theheads can print laterally or sideways. Referring to FIG. 7, a schematicof an alternate tandem color print head 600 is shown. The print head 600comprises a body 605 which defines a plurality of toner reservoirs suchas reservoir 610. A toner sump 620 is defined within the reservoir 610.A traveling wave guide member 630 transports toner from the sump 620 toa channel 645 through which gas such as air flows. A source of highpressure 640 is provided upstream of the location in the channel 645 atwhich toner from a reservoir is fed. The toner is entrained or otherwisecarried in the flowing gas stream in the channel 645 and subsequentlydeposited on a drum 650. Toner exits the channel 645 at exit or aperture612. The configuration of the other toner reservoirs generallycorresponds to that of toner reservoir 610.

FIG. 8 is a more detailed view of an individual flow cell having upperfluidization and lower return traveling wave grids. Specifically, FIG. 8illustrates a print head 700 defining a reservoir 710 which defines atoner sump 720. The print head 700 includes a body 705, a channel 745and pressure source 740. Toner is delivered from the sump 720 via atraveling wave grid 730 to an exit 712. Toner entrained in a flowing gasstream within the channel 745 is deposited upon a printing medium suchas drum 750. Specifically, the traveling wave grid 730 includes an uppertoner delivery leg 732 and a lower toner return leg 734.

In all of the exemplary embodiments described herein, a wide array ofdifferent configurations and arrangements of reservoir bodies, channels,high pressure gas sources, and traveling wave grids can be utilized. Thesystems described herein can employ one or more reservoirs inconjunction with a gas flow channel or member providing such.Alternately, each reservoir may be utilized with its own dedicated gasflow channel. Alternately, a plurality of sets of reservoirs andchannels can be used. For example, two or more sets of a pair ofreservoirs dedicated to a single channel can be used. FIG. 6 illustratesa pair of reservoirs and a dedicated channel.

Generally, the exemplary embodiment traveling wave grid assembliesinclude a traveling wave grid that is non-planar. Examples of suchgeometry include but are not limited to arcuate, curved, or linearlyalternating or stepped configurations. The non-planar grid is positionedwithin a reservoir such that upon operation of the grid, the grid servesto recirculate and provide a continuous supply of particulates ormaterial to a desired location. A significant advantage of thisconfiguration is that it can reduce, and in certain applications,entirely eliminate, mechanical moving parts, such as may otherwise berequired.

Experiments with several planar and non-planar traveling wave gridarrangements have shown that toner re-circulating transport is possiblefor the designed flow cells. In addition, the electrostatic fields fortransport of toner has been modeled and quantified. Electrodynamics oftoner gating have also been modeled and optimized to successfully guideexperiments.

The exemplary embodiment has been described with reference to thepreferred embodiments. Obviously, modifications and alterations willoccur to others upon reading and understanding the preceding detaileddescription. It is intended that the exemplary embodiment be construedas including all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

1. A reservoir system adapted for use in a printing system, thereservoir: system comprising: a reservoir body defining an interiorhollow region adapted to store particles and a channel, the hollowregion and the channel being in flow communication through a particlefeed exit; a traveling wave grid assembly disposed within the interiorhollow region, the traveling wave grid assembly adapted to transportparticles in the hollow region defined in the reservoir body to alocation proximate the particle feed exit, and the traveling wave gridassembly including a non-planartraveling wave grid that serves torecirculate and provide a continuous supply of particles to the locationproximate the particle feed exit.
 2. The reservoir system of claim 1further comprising: a high pressure gas source in flow communicationwith the channel defined in the reservoir body.
 3. The reservoir systemof claim 1 wherein the hollow region defines a first location proximatethe particle feed exit and a second location distal from the firstlocation, the traveling wave grid assembly including: a first travelingwave grid adapted to transport particles to the second location; and asecond traveling wave grid adapted to transport particles from thesecond location to the first location proximate the particle feed exit.4. The reservoir system of claim 1 wherein the traveling wave gridassembly includes: a roll member defining an outer circumferentialsurface; and a plurality of traveling wave electrodes disposed about theouter circumferential surface of the roll member.
 5. The reservoirsystem of claim 1 wherein the traveling wave grid assembly includes: aplurality of traveling wave electrodes disposed on a surface of thereservoir body defining the interior hollow region.
 6. A reservoirsystem adapted for use in a printing system, the reservoir systemcomprising: at least one member defining a hollow flow channelterminating at a channel exit; a plurality of reservoir bodies, eachreservoir body defining an interior hollow region adapted to storeparticles, the hollow region and the hollow flow channel being in flowcommunication through a particle feed exit; and a plurality of travelingwave grids, at least one of the plurality of traveling wave grids beingdisposed within the interior hollow region of a corresponding reservoirbody and positioned and configured to transport particles in the hollowregion of the corresponding reservoir body to a location proximate theparticle feed exit.
 7. The reservoir system of claim 6 wherein thesystem comprises four reservoir bodies, each in flow communication withthe hollow flow channel.
 8. The reservoir system of claim 6 wherein thesystem comprises two sets of a pair of reservoir bodies for a total offour reservoir bodies, two members each defining a hollow flow channel,each pair of reservoir bodies being in flow communication with thehollow flow channel of a respective member.
 9. The reservoir system ofclaim 6 further comprising: a source of high pressure gas, the sourcebeing in flow communication with the hollow flow channels defined in themembers.
 10. The reservoir system of claim 6 wherein the plurality oftraveling wave grids include a collection of traveling wave electrodes.11. A reservoir system adapted for use in a printing system, thereservoir system comprising: a plurality of reservoir bodies, each bodydefining an interior hollow region adapted to store particles; aplurality of corresponding gas channels, each gas channel dedicated to arespective reservoir body and in flow communication therewith through aparticle feed exit; and a plurality of corresponding traveling wavegrids, each traveling wave grid disposed in an interior hollow regiondefined within a respective reservoir body.
 12. The reservoir system ofclaim 11 further comprising: a high pressure gas source in flowcommunication with the plurality of gas channels.
 13. The reservoirsystem of claim 11 wherein each hollow region defined with a reservoirbody defines a first location proximate the particle feed exit and asecond location distal from the first location, each traveling wave gridincluding: a first traveling wave leg adapted to transport particles tothe second location; and a second traveling wave leg adapted totransport particles from the second location to the first locationproximate the particle feed exit.
 14. The reservoir system of claim 11wherein the plurality of traveling wave grids include: a substrate; aplurality of traveling wave electrodes; and at least one buss disposedon the substrate and in electrical communication with at least a portionof the plurality of traveling wave electrodes.